Process for production of sodium peroxide



United States Patent Cfiice 3,012,855 PROCESS FOR PRODUCTION OF SODIUM PEROXIDE William R. Babb, Albion, Pa., Jerome Champaign, Ill., and Charles H. von Tesmar, Ashtahula, Ohio, assignors to National Distillers and Chemical Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed May 18, 1959, Ser. No. 813,657 Claims. (Cl. 23-184) This invention relates broadly to an improved process for making sodium peroxide from sodium. More specifically, it relates to an improvement in the process for converting elemental sodium to sodium peroxidewhich has been described, for example, by Tadler and Coleman in US. Patent 2,789,885.

The process described in the prior art has many disadvantages, for instance, the production of a relatively large amount of fines or dust, the frequent formation of sticky reaction masses, and the contamination of the peroxide product with impurities, particularly iron, under the reaction conditions. Another objection the earlier process is the slow rate of oxidation. Although variations such as the use of higher oxygen concentrations and/or higher reaction temperatures may increase this rate, at the same time they increase the cost of operation in addition to presenting additional operation difiiculties.

One of the objects of this invention is to obtain superior and pure products by an improvement which makes possible a substantial increase in the sodium peroxide content of the product.

A further object is to provide a method for the manufacture of sodium peroxide wherein the amount of dust and fines in the product has been substantially reduced.

Another object is to decrease significantly the amount of iron and other contaminating materials in the sodium peroxide product.

Another object of the invention is to provide a practical, commercial process for the manufacture of sodium peroxide.

The above objects as well as others, which will become apparent from the following detailed description, may be conveniently achieved by this newly discovered improvement in the operation.

Until the present invention, the most satisfactory commercial method for the manufacture of sodium peroxide has been a process which includes (1) mixing elemental sodium with sodium peroxide in an inert atmosphere at a temperature above the melting point of sodium and below the temperature at which any substantial reaction occurs between sodium and sodium peroxide, (2) adding a controlled amount of moisture, (3) heating the resulting mixture to form sodium monoxide by a disproportionation reaction between the sodium and the sodium peroxide, and (4) converting the sodium monoxide to sodium peroxide in an oxidizing atmosphere.

This newly discovered process comprises (1) forming a suitable mixture of elemental sodium and sodium peroxide by agitating a mixture of these materials in an inert atmosphere at a temeprature above the melting point of sodium and at which there is no substantial reaction between sodium and sodium peroxides, (2) adding a critical, controlled amount of moisture, and (3) heating the resulting mixture of sodium and sodium peroxide in the presence of an oxygen-containing gas to convert the sodium to sodium peroxide. Thus, the intermediate formation of the sodium monoxide in a separate step is completely eliminated.

The process of the present invention is considerably easier to operate and to control than other processes G. Andrews,

which include an intermediate reduction step, ease of control being of particular importance when handling sodium. The present process also results in consistently better product quality; the quantity of objectionable dusts, fines, and contaminants, especially iron, has been reduced significantly. The complete elimination of the reduction step has also conspicuously lowered operating and maintenance costs and raised production capacity.

'In accordance with the present invention, a mass of finely-divided sodium peroxide is provided and preferably maintained in a state of continuous movement and/or agitation. The temperature of this first mixing step should be above the melting point of sodium and below the temperature at which there is any substantial reaction between the sodium and the sodium peroxide, that is, the temperature should be between about and, 205 C., and preferably between about 100 and C. An atmosphere is maintained which is substantially free from oxygen and substantially inert with respect to both sodium and sodium peroxide. There is then added to the sodium peroxide a minor portion of elemental sodium, that is, about 1 to 10 weight percent based on the sodium peroxide, and preferably about 3 to 8 weight percent. Under these conditions the sodium does not react with the sodium peroxide, but instead it becomes intimately admixed with the sodium peroxide particles.

The sodium-sodium peroxide mixture is then transferred from the mixing zone to the oxidizing zone. A controlled amount of water vapor is added to the sodiumsodium peroxide mixture preferably before the oxidation commences, although it may be added at any time after mixing is essentially complete. It may be added, for example, (1) in the mixer after mixing, (2) between the mixer and the oxidizer, or (3) in the oxidizer substantially before the contact with the oxidizing gas. The amount of water vapor added should be equivalent to from about 0.03 to about 1.3 weight percent based on the sodium present, and preferably from about 0.1 to 0.4 weight percent. The solid reactant material should be thoroughly agitated in order to expose the sodium-sodium peroxide mixture as uniformly as possible to the water vapor. The required amount of water vapor may be satisfactorily introduced into the system by means of a controlled stream of moist air, nitrogen, or other suitable gas having a definite dew point for the purpose of critical control of the moisture content. For example, satisfactory results are obtained by the addition of about 12 to 25 cubic feet per minute of humidified air, and preferably about 15 to 19 cubic feet per minute, with corresponding dew points of about 20 to 75 'F., and preferably about 30 to 45 F. More or less carrying gas may be used, the prime requisite being that the amount of moisture-carrying gas be sufficient to insure good contact of the water vapor with the solids.

In the oxidizer where the sodium is converted to sodium peroxide, the reacting material is maintained within thetemperature range of about 260 to 450 C., preferably about 315 to 400 C., and the mass is continuously contacted with a dry, oxygen-containing gas, such as for example dry air, oxygen-enriched air, or relatively pure oxygen. Either atmospheric or superatmospheric pressures can be employed. The solids should be thoroughly agitated to insure good contact with the oxidizing gas which is prefer-ably used in excess to insure complete oxidation.

The sodium peroxide thus prepared is discharged from the oxidizer, screened, and the portion having the desired particle size withdrawn as commercial product, while the remainder is recirculated to the mixing step as feed thereto.

The following table is included to demonstrate the advantages of the present process, i.e., mixing and oxidiz- Patented Dec. 12, 1961 ing, over the earlier process of mixing, reducing, and oxidizing, that is,'to demonstrate the advantages gained by the process of the instant process whereby the reduction step is eliminated.

(a) and ((1) represent separate, but similar runs.

Thus it can. be seen that the elimination of the reduction step resulted in the following major improvements: (1) the amount of product containing more than 98 percent sodium peroxide has increased from about 2 percent up to about 20-40 percent, and'the amount of product contain-ing above 97 percent sodium peroxide has increased from about 55 percent to about 8595' percent; (2) the iron contamination has been reduced from an average of approximately 50 p.p.m. to only about 20-30 p.p.m.; and (3) the quan ity of undesired fines in the oxidizer (final) product has been decreased from an average of about 9 percent to about 35 percent.

To summarize, the elimination of the reduction step in the process for converting sodium to sodium peroxide has resulted in the following unexpected and highly desirable advantages:

(l) The plant operation is easier to handle and control, resulting in more economical operation and better product quality. V

(2) The percentage of impurities, especially of iron, has

been reduced drastically.

(3) The amount of dust and fines has been reduced significantly, resulting in both improved product quality and higher yield.

(4) The total time required to produce commercial 3 grade sodium peroxide is substantially shortened.

(5) Plant maintenance and operating costs have been lowered, while production capacity has been increased due to decreased production downtime.

In order to describe this invention further, the follow- 0 ing example is set forth solely for purposes of illustration and is not intended to limit the invention in any manner except in accord with the appended claims.

Example The data presented in Table II were obtained during continuous runs made while operating the process of the invention (runs A and B). Data from run C,.obtained while operating the process for obtaining sodium peroxide using the reduction step, are included for'purposes of comparison. -In runs A and B sodium was admixed with sodium peroxide, moist air was added, and the resulting mixture was treated with dry air to oxidize the sodium to sodium peroxide. In run C the sodium and sodium peroxide were mixed, moist air added, the mixture heated to convert the mixture to sodium monoxide-sodium peroxide, and the resulting mixture treated with an oxidizing medium to convert the sodium monoxide to sodium peroxide.

TABLE 11 .Run A Bun B Run 0 Feed Rates:

Sodium, #lhr. (av.) 365 350 250 Sodium peroxide, #lhr. (av.) 7, 200 6, 800 4, 450 Moist air:

Flow rate, c.t.m 19 17 .22. 0 Dew Point, F 35 45- 49-64 Product Analysis:

- NaQOz, percent by wt- 97. 4-984 97. 5-98. 6 97. 3-97. 1 FeiOZ, p.p.m 18-22 16-22 79-81 Fines, percent by wt 4-5 3-4 8-9 Temperature, "0.:

Mixerinlet 103418 102-120 102-116 discharge. 123442 -145 fi l-.141 Redueerinlet 171-196 center 188-218 discharge 404441 Oxidizer 330-400 325-390 399-429 What is claimed is: a

1. An improved process for'the production of sodium peroxide whereby the amount of fines is reduced at least 40 percent, the amount of iron impurities is reduced at least 45 percent, and the amount of sodium peroxide product having a purity above 98 percent is increased at least 1,000 percent which'comprises (-1) contacting finelydivided sodium peroxide with sodium in an atmosphere substantially inert with respect to sodium and sodium peroxide at a temperature above the melting point of sodium and below the temperature at which sodium reacts substantially with sodium peroxide, (2) adding water vapor in an amount of from about 0.03 to about 1.3 weight percent based on the amount of sodium prior to the final oxidation step, and (3) contacting the resulting mixture with an oxidizing atmosphere to form particles consisting essentially of sodium peroxide.

2. The process of claim 1 wherein the water vapor is added in an amount of from 0.1 to 0.4 weight percent basedon the amount of sodium.

3. The process of claim 1 wherein the sodium peroxide is contacted with about 1 to about 10 weight percent of sodium based on the amount of sodium peroxide.

4. The'process of claim 1 wherein the sodium and sodium peroxide are mixed at a temperature between about 100 and 205 C. and the resulting mixture is subjected to: an oxidizing atmosphere at about 260 to 450 C.

5. In an improved process for the production of sodium peroxide whereby the amount of fines is reduced at least 40 percent, the amount of iron'impurities is reduced at least 45 percent, and the amount of sodium peroxide product having a purity above 98 percent is increased at least 1,000 percent and which comprises (1) contacting finelydivided sodium peroxide with sodium in an inert atmosphere at a temperature above the melting point of sodium and below the temperature at which sodium reacts substantially-with sodium peroxide, (2) adding controlled amounts of water vapor from about 0.03 to about 1.3 weight percent based on the sodium prior to the final oxidation step, and (3) contacting the resulting mixture with an oxidizing atmosphere, the improvement which comprises carrying'out the' oxidizing step (3) directly after the mixing step (1).

Referenees Cited in the file of this patent H UNITED STATES PATENTS' 2,789,885 Tadler et a1 Apr. 23, 7 

1. AN IMPROVED PROCESS FOR THE PRODUCTION OF SODIUM PEROXIDE WHEREBY THE AMOUNT OF FINES IS REDUCED AT LEAST 40 PERCENT, THE AMOUNT OF IRON IMPURITIES IS REDUCED AT LEAST 45 PERCENT, AND THE AMOUNT OF SODIUM PEROXIDE PRODUCT HAVING A PURITY ABOVE 98 PERCENT IS INCREASED AT LEAST 1,000 PERCENT WHICH COMPRISES (1) CONTACTING FINELYDIVIDED SODIUM PEROXIDE WITH SODIUM IN AN ATMOSPHERE SUBSTANTIALLY INERT WITH RESPECT TO SODIUM AND SODIUM PEROXIDE AT A TEMPERATURE ABOVE THE MELTING POINT OF SODIUM AND BELOW THE TEMPERATURE AT WHICH SODIUM REACTS SUBSTANTIALLY WITH SODIUM PEROXIDE, (2) ADDING WATER VAPOR IN AN AMOUNT OF FROM ABOUT 0.03 TO ABOUT 1.3 WEIGHT PERCENT BASED ON THE AMOUNT OF SODIUM PRIOR TO THE FINAL OXIDATION STEP, AND (3) CONTACTING THE RESULTING MIXTURE WITH AN OXIDIZING ATMOSPHERE TO FORM PARTICLES CONSISTING ESSENTIALLY OF SODIUM PEROXIDE. 